Many types of equipment require manual adjustments for varying certain parameters thereof. One particular application wherein such adjustments are a common occurrence is adjustment of the "angle of attack" or elevation of a screed of an asphalt paving machine as required to produce the desired depth or thickness of the paving material being laid by the paver. Such thickness control of an asphalt paver traditionally consists of manipulation of a hand-crank. Turning the hand-crank rotates a threaded shaft which causes the change in the "angle of attack" of the screed and thus changes the depth or thickness of the paving material being placed by the paver.
More specifically, turning the hand-crank clockwise causes the elevation of the screed to be raised or lowered, as the case may be, whereas turning the hand-crank counterclockwise causes a change in elevation of the screed opposite to that obtained with the clockwise rotation.
Operators of asphalt pavers generally have a strong preference as to which direction of hand-crank rotation raises the screed. Some operators prefer clockwise rotation of the hand-crank for increasing the thickness of the paving material, while others prefer counter-clockwise rotation for the same effect.
For that reason, the threaded shaft rotated by the hand-crank is generally provided with two different configurations: a left-hand (LH) version having "left-hand" threads and a right-hand (RH) version having "right-hand" threads. Thus, the desired rotational action is obtained by utilizing equipment with a hand-crank and screw arrangement having the desired handedness.
Unfortunately, an operator's preferred handedness may not be known until the paving machine is put into service. Under those circumstances, if the handedness is incorrect for the operator, the obvious alternative is to change the handedness of the control screw in the field, generally at considerable expense and inconvenience. Further, if two operators use the same paver, each operator having a different handedness preference, such as one operator being left-handed and the other being right-handed, then one of the operators is satisfied with the handedness provided for controlling the elevation of the screed whereas the other operator is not.
What is needed is a thickness control mechanism that interchangeably provides either left-handed rotation action or right-handed rotation action for elevating the screed and, further, which can be quickly and easily field converted from one type of handedness to the other.